Caught my eye as I was driving by and I thought it would be a great cache location.
The Gregorian calendar is today's internationally accepted civil calendar and is also known as the "Western calendar". It was named after the man who first introduced it in February 1582: Pope Gregory XIII.
The calendar is strictly a solar calendar based on a 365-day common year divided into 12 months of irregular lengths. Each month consists of either 30 or 31 days with 1 month consisting of 28 days during the common year. A Leap Year usually occurs every 4 years which adds an extra day to make the second month of February 29 days long rather than 28 days.